Arguments: a message-number (optional), which, if present, may NOT refer to a message marked as deleted Restrictions: may only be given in the TRANSACTION state. Discussion: If an argument was given and the POP3 server issues a positive response with a line containing information for that message. This line is called a "unique-id listing" for that message. If no argument was given and the POP3 server issues a positive response, then the response given is multi-line. After the initial +OK, for each message in the maildrop, the POP3 server responds with a line containing information for that message. This line is called a "unique-id listing" for that message. In order to simplify parsing, all POP3 servers are required to use a certain format for unique-id listings. A unique-id listing consists of the message-number of the message, followed by a single space and the unique-id of the message. No information follows the unique-id in the unique-id listing. The unique-id of a message is an arbitrary server-determined string, consisting of one to 70 characters in the range 0x21 to 0x7E, which uniquely identifies a message within a maildrop and which persists across sessions. This persistence is required even if a session ends without entering the UPDATE state. The server should never reuse an unique-id in a given maildrop, for as long as the entity using the unique-id exists. Note that messages marked as deleted are not listed. While it is generally preferable for server implementations to store arbitrarily assigned unique-ids in the maildrop, this specification is intended to permit unique-ids to be calculated as a hash of the message. Clients should be able to handle a situation where two identical copies of a message in a maildrop have the same unique-id. Possible Responses: +OK unique-id listing follows -ERR no such message Examples: C: UIDL S: +OK S: 1 whqtswO00WBw418f9t5JxYwZ S: 2 QhdPYR:00WBw1Ph7x7 S: . ... C: UIDL 2 S: +OK 2 QhdPYR:00WBw1Ph7x7 ... C: UIDL 3 S: -ERR no such message, only 2 messages in maildrop |